How to use LIS3DHTR Accelerometer? How connect pins?

Other Hardware Sensors
1

I want use LIS3DHTR in one of my projects. I have problem with some pins of this sensor.

ADC pins: I want to connect some sensors with wire to jumper, Is it OK? Datasheet said we can connect ADC pins to Vdd, GND or leave float (If we don't want use them). Should I pull-up or pull-down them or using jumper? What is best solution?

SDO/SA0 pin: I want to use I2C for communication with MCU, for change I2C address is this jumper and pull-up OK? Is there any problem for this pin?

RES pin: What is this pin? Datasheet said to connect RES pin to GND.

INT pins: Interrupt pins are connect to MCU directly or need anything?

Vdd_IO pin: Datasheet said to connect some Caps (10uF and 100nF) between Vdd and GND, Connect 2 extra Caps for Vdd_IO make problem or no? Is it good for circuit or no?

If there is some problem or suggestion, I would be happy if you tell me.

Thanks a lot.

image
image1009×537 38.5 KB

2

The circuit looks fine but the extra ADC inputs need setting up correctly in software. This is an extract from the data sheet.

Auxiliary ADC and temperature sensor

The LIS3DH contains an auxiliary ADC with 3 separate dedicated inputs: pins ADC1, ADC2, ADC3.

The user can retrieve the converted data from registers OUT_ADC1_L (08h), OUT_ADC1_H (09h), OUT_ADC2_L (0Ah), OUT_ADC2_H (0Bh) and OUT_ADC3_L (0Ch), OUT_ADC3_H (0Dh).

In order to use the auxiliary ADC, the user must set the BDU bit (bit 7) to 1 in CTRL_REG4 (23h) and the ADC_EN bit (bit 7) to 1 in TEMP_CFG_REG (1Fh). The ADC sampling frequency is the same as that of the ODR in CTRL_REG1 (20h).

The input range is 1200 mv ±400 mV and the data output is expressed in 2's complement left-aligned.

The ADC resolution is 10 bits if the LPen (bit 3) in CTRL_REG1 (20h) is cleared (high- resolution / normal mode), otherwise, in low-power mode, the ADC resolution is 8-bit.

Channel 3 of the ADC can be connected to the temperature sensor by setting the TEMP_EN bit (bit 6) to 1 in TEMP_CFG_REG (1Fh). Refer to Table 5: Temperature sensor characteristics for the conversion factor.

3

Thanks

4

The reason for separate VDD and VDD_IO is so that the IO can operate at a different voltage from the internals of the chip.

You would only need separate decoupling on VDD and VDD_IO when they are separate supplies.

5

So can I remove C3 and C4?
Does their presence cause problems?

6

No not at all.

7

Did you study the device datasheet?

image
image974×792 47.1 KB

Probably

Probably not.

As always, the decoupling caps should be placed as close as possible to the chip pins (as the datasheet says), so you might put C1 close to VDD, and C3 close to VDD_IO - depends on how good your tracking is...

8

Are you using a chip or is it a board that contains this chip? If the latter these decoupling capacitors might already be on the board.

Note that C1 and C3 ( if you use both ) must be of the ceramic type or it will not do what it is designed to do and that is suppress high frequency noise.